In the Monk/Mowbray days I would say the main reason for underperformance was the quality of the signings. Signing average/poor players for big fees on big salaries.....and each team will have a combination of those players, and that's why looking at individuals, like Ayling, rather than as a total doesn't make sense.
It's also not 100% accurate, so why during the Monk days we under performed, or Ipswich and Sunderland have over performed over recent seasons.
We don't have that problem now. In fact we have the opposite.
Performance vs Budget is a combination of quality of recruitment and quality of coaching/management.
It's not just a reflection of the manager.
A lot of people think we are getting the recruitment right